JP7064836B2 - Metal scrap discrimination method using laser inductive plasma emission spectrometry, metal scrap discrimination device and metal scrap sorting system - Google Patents

Description

The present invention relates to a metal scrap discrimination method using a laser-induced plasma emission spectrometry method, a metal scrap discrimination device, and a metal scrap sorting system.

In recent years, in order to tackle the problem of waste and recycling and build a sound material-cycle society that balances the environment and the economy, the so-called 3Rs (reduce), Reuse (reuse) and Recycle (recycling) It is required to promote the 3Rs). Among them, regarding the recycling of metal scraps, for example, in the case of aluminum alloy scraps, conventionally, after the recovered aluminum products are melted to determine the contained elements, they are used for secondary alloys for castings and die castings. Cascade recycling is the mainstream.

Here, since the added elements of aluminum alloy scrap are different for each product, if the original alloy type can be identified before melting, so-called "product to product" horizontal recycling becomes possible, and the reuse rate of aluminum alloy scrap is large. Can be expected to improve.

For that purpose, a method for analyzing the constituent elements of aluminum alloy scrap in a short time and with high accuracy is required.

Laser-induced plasma spectroscopy (LIPS) is an analytical method that is being studied for application to the analysis of component elements of metal scrap. LIPS is a method of performing elemental analysis of a sample based on the spectral line intensity by spectroscopically analyzing the plasma generated when the sample is focused and irradiated with a high-power pulse laser. LIPS can be analyzed directly in the atmosphere without pretreatment of the sample, and has the feature that simultaneous analysis of multiple elements can be performed instantly with a simple operation, which is an effective analysis method as an on-site analysis method.

In order to apply LIPS to the component analysis of metal scrap, problems such as fluctuations in spectral line strength and variation in analysis results due to the shape of the scrap are solved, and metal scrap from many alloy types based on the analysis results. It is necessary to establish a method for discriminating the alloy type of.

Examples of attempts to apply LIPS to the component analysis of metal scrap include the techniques disclosed in Patent Document 1 and Non-Patent Document 1.

Japanese Unexamined Patent Publication No. 2016-209812

Laser Induced breakdown spectroscopy for fast elemental analysis and sorting of metallic scrap pieces using certified reference materials. (Spectrochim. Acta Part B 74-75, 46-50 (2012).

In each of the above-mentioned techniques, in order to accurately focus the laser on the sample surface, a system for measuring the distance to the scrap and a moving means for the focusing means are provided, and the laser is focused according to the distance to the scrap. The means is moved to irradiate the laser.

Therefore, the analyzer has a complicated structure. In addition, since there is no means for suppressing variations in analysis results, it is necessary to increase the number of laser irradiations.

Therefore, in the present invention, the metal scrap using the laser-induced plasma emission spectrometry method, which can analyze the component elements without being affected by the shape of the metal scrap and the like and can accurately determine the alloy type, is used. The purpose is to provide a discrimination method. Another object of the present invention is to provide a discrimination device capable of carrying out the method and a metal scrap sorting system capable of sorting metal scrap based on the discrimination result.

In order to achieve the above object, the invention according to claim 1 is a method for discriminating metal scraps using a laser-induced plasma emission analysis method, in which a laser for generating laser-induced plasma in the metal scraps to be discriminated is generated. The process of condensing and irradiating light, the process of dispersing the emitted light from the laser-induced plasma generated by the irradiation of laser light and acquiring the emission spectrum, and the spectral lines of the component elements used for preset discrimination. A step of calculating the concentration of the component element based on the intensity and a step of discriminating the alloy type to be discriminated based on the concentration of each component element are provided, and the laser light to be irradiated is focused on the metal scrap. The focal distance is a long focal length in which the influence of the fluctuation of the distance between the metal scrap surface and the light source of the laser beam due to the variation in the shape of the metal scrap on the fluctuation of the energy density of the laser beam is small, and the energy of the laser beam is small. The density is fixed at a distance that is the energy density at which the concentration of the component element can be analyzed, and the concentration of the component element is the intensity ratio between the spectral line intensity of the component element and the spectral line intensity of the main component to be discriminated. The technical means of calculating based on is used.

In the invention according to claim 2, in the method for discriminating metal scrap according to claim 1, the energy density of the laser beam to be irradiated is measured by the breakdown plasma of the atmospheric gas in the measurement environment to measure the spectral line intensity of the component element. The technical means of being set to an energy density that does not interfere is used.

In the invention according to claim 3, in the method for discriminating metal scrap according to claim 1 or 2, the technical means that the metal scrap is an aluminum alloy is used.

In the invention according to claim 4, in the method for discriminating metal scrap according to claim 3, the technical means that the component elements used for discriminating are Si, Zn, Cu, Mg and Mn is used.

In the invention according to claim 5, in the method for discriminating metal scrap according to claim 4, the corresponding concentrations of Si, Zn, Cu, Mg and Mn are dealt with in this order based on the discrimination conditions set at each concentration. The technical means of sequentially determining the alloy type to be used is used.

The invention according to claim 6 is a metal scrap discrimination apparatus that discriminates metal scrap by using a laser-induced plasma emission analysis method, wherein a laser oscillator that outputs laser light and a laser beam output from the laser oscillator are used. The objective lens that concentrates and irradiates the metal scrap to be discriminated, the condensing means that condenses the radiated light emitted from the laser-induced plasma that is irradiated with the laser light and generated from the metal scrap, and the condensing means. Based on the spectroscope that disperses the emitted emitted light and acquires the emission spectrum and the spectral line intensity of the emission spectrum acquired by the spectroscope, the concentration of the component element used for the preset discrimination is calculated. It is provided with an arithmetic processing means for determining the alloy type of the metal scrap, and the focal distance of the objective lens is such that the fluctuation of the distance between the metal scrap surface and the light source of the laser light due to the variation in the shape of the metal scrap is the laser light. It is a long focal point that has a small effect on the fluctuation of the energy density, and is set to a fixed distance at which the energy density of the laser light becomes the energy density at which the concentration analysis of the component elements is possible, and claims 1 to claim 1 to claim. The technical means that the method for discriminating metal scrap according to any one of 5 is configured to be feasible is used.

In the invention according to claim 7, the metal scrap sorting system transfers the metal scrap to the metal scrap discriminating device according to claim 6 and the metal scrap discriminating device, and discriminates the alloy type. A technical means is used which includes a transport device carried out from the metal scrap discriminating device and a sorting device for sorting the metal scrap carried out from the metal scrap discriminating device according to the alloy type.

According to the invention according to claim 1, in the method for discriminating metal scrap using a laser-induced plasma emission analysis method, the focal distance for concentrating the irradiated laser light on the metal scrap corresponds to the variation in the shape of the metal scrap. However, since the energy density of the laser beam is set to a distance that makes it possible to analyze the concentration of the constituent elements, the change in the area of the irradiated laser beam is small with respect to the change in the height of the metal scrap. Therefore, fluctuations in energy density can be reduced. Further, the intensity ratio between the spectral line intensity of the component element and the spectral line intensity of the main component to be discriminated is hardly affected by the height of the metal scrap. As a result, it is possible to analyze the constituent elements with almost no influence on the shape of the metal scrap and the like, and it is possible to accurately determine the alloy type.

As in the invention of claim 2, it is preferable that the energy density of the laser beam to be irradiated is set to an energy density at which the breakdown plasma of the atmospheric gas in the measurement environment does not hinder the measurement of the spectral line intensity of the constituent elements. As a result, the spectral line intensity can be increased, and the ratio LBR (Line-to-background ratio) with the background can be increased, so that the analysis accuracy can be improved.

The method for discriminating metal scrap of the present invention can be suitably used for discriminating metal scrap made of an aluminum alloy as in the invention according to claim 3. This is because Al has few spectral lines and can be easily separated from the spectrum of the component element used for discriminating the alloy type.

In the present invention, a discrimination method utilizing the difference in the concentration of the main additive elements characteristic of the alloy system of the aluminum alloy is adopted, and as in the invention of claim 4, the component elements used for discrimination are Si and Zn. , Cu, Mg and Mn. Further, as in the invention of claim 5, a discrimination method for discriminating the corresponding alloy type based on each concentration was adopted in the order of Si, Zn, Cu, Mg and Mn. According to this, first, the cast material and the wrought material can be discriminated, and then the wrought material can be sequentially discriminated as each alloy system, and the alloy type can be efficiently discriminated.

According to the sixth aspect of the present invention, it is possible to provide a metal scrap discriminating device for discriminating an alloy type of metal scrap by the metal scrap discriminating method of the present invention.

According to the invention of claim 7, by combining the metal scrap discriminating device with the transport device and the sorting device, the alloy type of the metal scrap is discriminated by the metal scrap discriminating method of the present invention, and the metal is sorted for each alloy type. A scrap sorting system can be constructed.

It is a schematic explanatory drawing of the structure of a metal scrap sorting system. It is a schematic explanatory drawing of the structure of the metal scrap discrimination apparatus. It is a flowchart for discriminating aluminum alloy scrap. It is explanatory drawing which shows an example of the emission spectrum of an aluminum alloy. It is a flowchart for discriminating the alloy type of aluminum alloy scrap. It is a figure which shows an example of the emission spectrum observed when the laser light energy is 30 mJ, 60 mJ and 90 mJ. It is a figure which shows the result of having measured the spectral line intensity and the background of copper in order to evaluate the influence of the laser light energy on the emission spectrum. It is the figure which plotted the ratio LBR of the spectral line intensity and the background with respect to the laser light energy. It is a figure which shows the measurement of the spectral line intensity when the height of a sample is changed. (a) is the spectral line Cu I 521.8 nm of the constituent element copper, and (b) is the spectral line Al I 396.1 nm of the parent aluminum. It is a figure which shows the spectral line intensity ratio of copper and aluminum at each sample height. It is a figure which shows the calibration curve of Cu. (a) is a calibration curve when Cu I 521.8 nm is used as the spectral line for analysis, and (b) is a calibration curve when Cu I 324.7 nm is used as the spectral line for analysis. It is a figure which shows the calibration curve of Si, Zn, Mg and Mn respectively. It is a photograph which shows the aluminum alloy scrap sample used for the sorting test.

The method for discriminating metal scrap, the metal scrap discriminating device, and the metal scrap sorting system according to the present invention will be described with reference to the drawings. Hereinafter, a method for discriminating aluminum alloy scrap will be described as an example.

(Structure of metal scrap discrimination device and metal scrap sorting system)
As shown in FIG. 1, the metal scrap sorting system S includes a metal scrap discriminating device 1, a transport device 2, and a sorting device 3.

The transport device 2 transports the metal scrap M to be discriminated to the metal scrap discriminating device 1, and carries out the metal scrap M after discriminating the alloy type from the metal scrap discriminating device 1. As the transport device 2, a known transport means equipped with a belt conveyor, a rotary stage, or the like can be adopted. Here, the transport device 2 may store the metal scrap M one by one and provide a movable cell or the like.

Further, the transport device 2 uses a synchronous signal of the repetition frequency of the laser pulse transmitted from the pulse generator 15 (FIG. 2) of the metal scrap discriminating device 1 to match the timing of laser light irradiation by the metal scrap discriminating device 1 to match the metal scrap. It is also possible to adopt a STOP / GO method in which M is determined in a stationary state and then moved. According to this, since the laser beam is irradiated in a stationary state, elemental analysis with good reproducibility can be performed, so that the discrimination accuracy can be improved. Further, it is easy to sort the metal scrap M after the discrimination.

The sorting device 3 sorts the metal scrap M carried out from the metal scrap discriminating device 1 for each alloy type based on the discriminating result of the alloy type to be discriminated sent from the metal scrap discriminating device 1.

The metal scrap discriminating device 1 is a device that discriminates metal scrap by using a laser-induced plasma spectroscopy (LIPS).

As shown in FIG. 2, the metal scrap discriminating device 1 includes a laser oscillator 10 that outputs a laser beam L for generating a laser-induced plasma P in the metal scrap M to be discriminated, and a laser output from the laser oscillator 10. An objective lens 11 that condenses and irradiates the metal scrap M to be discriminated with light L, and a condensing means 12 that condenses the emitted light emitted from the laser-induced plasma generated from the metal scrap M by being irradiated with the laser light L. , Used for preset discrimination based on the spectroscope 13 that disperses the emitted light collected by the condensing means 12 and acquires the emission spectrum and the spectral line intensity of the emission spectrum acquired by the spectroscope 13. It is provided with a processing system 14 that calculates the concentration of component elements, discriminates the alloy type to be discriminated, and controls the metal scrap discriminating device 1.

As the laser oscillator 10, an oscillator that oscillates a Nd: YAG pulse laser (pulse width 10 ns) of a fundamental wave having a wavelength of 1064 nm was adopted. In this embodiment, the pulse energy is adjusted to 10-100 mJ / pulse and the repetition frequency is 10 Hz. Here, the repetition frequency can be set to a frequency that the carrier 2 can respond to.

As the objective lens 11, a long focal length, for example, a convex lens having a focal length of 600 mm is used instead of a convex lens having a focal length of about several -20 cm, which is usually used in LIPS. This makes it possible to analyze metal scrap M of various sizes and shapes.

In addition, when a short-focus objective lens is used, the area of the irradiated laser beam changes significantly with respect to the change in the height of the metal scrap M, so that the fluctuation in energy density becomes large, and accurate analysis can be performed. I can't. In addition, as the defocusing increases, the energy density decreases significantly, so that the spectral line intensity of the emission spectrum decreases, making it difficult to perform analysis. For example, in "Effects of laser defocus on the emission characteristics of laser-generated plasma" (Chubu University Faculty of Engineering, Vol. 31, p.79 (1995), laser light is focused by an objective lens with a focal length of 50 mm and focused. It has been reported that when the amount of deviation is changed by −7 mm − + 7 mm, the spectral line intensity is significantly reduced within the range.

Therefore, in the conventional LIPS, it is necessary to move the objective lens according to the height of the metal scrap M. In the present invention, since the long-focus objective lens 11 is adopted, the change in the area of the irradiated laser beam can be made small with respect to the change in the height of the metal scrap M, so that the change in energy density can be made. Can be made smaller. As a result, accurate analysis can be performed without moving the objective lens according to the height of the metal scrap M, and it is not necessary to provide a moving mechanism for the objective lens.

The light collecting means 12 collects the synchrotron radiation emitted from the metal scrap M and inputs it to the spectroscope 13. Here, it is preferable that the light collecting means 12 is arranged close to the incident optical axis of the laser beam L. This is because a part of the synchrotron radiation is always generated in the direction of the laser optical axis, so that the synchrotron radiation can be reliably measured even when the surface of the metal scrap M is inclined. In the present embodiment, an optical fiber is used as the condensing means 12, but a mirror or a condensing lens can be used instead of the optical fiber.

The spectroscope 13 has a built-in detector, disperses the synchrotron radiation collected by the condensing means 12, acquires an emission spectrum, and sends it to the processing system 14. Here, in order to discriminate the metal scrap of the aluminum alloy by the metal scrap discriminating device 1, the measurement wavelength is measured so that the spectra of Al, Si, Zn, Cu, Mg and Mn, which are the component elements necessary for discriminating, can be measured. Use a wide range of spectroscopes. For example, a spectroscope capable of simultaneously measuring spectral lines of multiple elements having a measurement wavelength range of about 200 to 700 nm is adopted.

The processing system 14 includes a calculation unit 14a and a control unit 14b, which are calculation processing means.

The calculation unit 14a is a calibration curve showing the relationship between the spectral line intensity and the concentration, which is experimentally obtained in advance in order to acquire the concentration of each measurement target component from the spectral line intensity of the emission spectrum acquired by the spectroscope 13. The line is remembered. The calibration curve is created for each component element necessary for discriminating the alloy type of the metal scrap M, and in this embodiment, the calibration curves of Si, Zn, Cu, Mg and Mn are stored respectively.

The calculation unit 14a calculates the concentration of the component element of the metal scrap M using the calibration curve, and discriminates the alloy type to be discriminated. The discriminant result of the alloy type of the metal scrap M is sent to the sorting device 3.

The control unit 14b controls the metal scrap discriminating device 1 such as the output of the laser beam L.

(Method of identifying metal scrap)
The method for discriminating metal scrap according to the present invention will be described by taking as an example a method for discriminating aluminum alloy scrap.

First, the metal scrap M adjusted to a size that can be discriminated by the metal scrap discriminating device 1 is transported to the metal scrap discriminating device 1 by the transport device 2. Here, as the transport device 2, a transport device including a cell for storing metal scrap M one by one will be described as an example.

When the cell in which the metal scrap M is stored reaches the measurement position of the metal scrap discriminating device 1, the transport device 2 stops the transport.

FIG. 3 shows a flowchart for discriminating aluminum alloy scrap. In step S1, the laser beam L for generating the laser-induced plasma P output from the laser oscillator 10 is focused by the objective lens 11 and irradiated to the metal scrap M. Here, the energy density of the laser beam L to be irradiated is set to an intensity at which the breakdown plasma of the atmospheric gas in the measurement environment, or the atmosphere in the present embodiment, does not hinder the measurement of the spectral line intensity of the component element. As a result, the spectral line intensity can be increased, and the ratio LBR (Line-to-background ratio) with the background can be increased, so that the analysis accuracy can be improved.

In the following step S2, the synchrotron radiation from the laser-induced plasma P generated by the irradiation of the laser beam L is separated by the spectroscope 13 to acquire an emission spectrum. The emission spectrum data is sent to the processing system 14. FIG. 4 shows an example of the emission spectrum.

In the following step S3, the concentration of the component element is calculated based on the spectral line intensity of the component element used for the preset discrimination. When the metal scrap M is irradiated with laser light, laser-induced plasma is generated. When the component element transitions from the excited state to the lower level, it emits plasma light having a wavelength peculiar to the component element. Since the intensity of synchrotron radiation is substantially proportional to the number of atoms, the concentration of the component element can be calculated from the spectral line intensity of the wavelength peculiar to the component element.

The calculation of the concentration of the component element is performed in the calculation unit 14a of the processing system 14, as shown in FIGS. 11B and 12, the calibration curve of Si, Zn, Cu, Mg and Mn stored in the calculation unit 14a. Do based on. The calibration line is created by plotting the relationship between the concentration of each component element and the spectral line intensity using a standard sample. The intensity ratio of is plotted on the vertical axis and the concentration of the constituent elements is plotted on the horizontal axis.

Here, since the metal scrap M has various shapes, the height is different and the observed spectral line intensity changes. As shown in the examples, the changes in the spectral line intensities of the component elements and aluminum show almost the same tendency. Therefore, by taking the ratio between the two, the changes in the spectral line intensities due to the difference in the sample height can be obtained. It can be corrected. As a result, the shape of the metal scrap M (for example, unevenness) is not easily affected, and measurement can be performed with high accuracy. Therefore, we decided to use the intensity ratio of the spectral lines of the constituent elements and the spectral lines of the parent aluminum for the analysis of the concentration of the constituent elements. As a result, the variation in the spectral line intensity can be made extremely small, so that accurate analysis can be performed by irradiating the laser beam only once.

In the following step S4, the alloy type to be discriminated is discriminated based on the concentration of each component element.

Aluminum alloys are roughly classified into castings / die-casting materials and wrought materials, and wrought materials are classified into eight types of alloys, 1000-8000 series, according to the types of major additive elements (JIS H 4000: 2014). .. Here, since the concentrations of the added elements are different for each alloy system even in the same alloy system, it is necessary to set a certain component standard for each alloy system in scrap sorting.

Table 1 shows an example of the component standard. Considering the actual reuse of aluminum alloy scrap, it is classified into 6 types of alloys, and the 4000 series alloys of casting / die casting material and wrought material are reused for ADC12 of casting / die casting material.

Aluminum alloy scrap is sorted by comparing the analytical values of the constituent elements of the concentration with the constituent standard values of each alloy system. Here, the method for determining all the constituent elements is not necessarily an effective selection method. This is because the spectral line intensity of the low-concentration element is weak and easily affected by the background, and if the low-concentration element is included in the determination element, it may not be possible to discriminate.

In the present invention, we have found a discrimination method for efficient discrimination by utilizing the difference in the concentration of the main additive element characteristic of each alloy system. FIG. 5 shows a flowchart for discriminating the alloy type of the aluminum alloy.

First, using the difference in Si concentration between the cast material and the wrought material, the lower limit of the Si concentration (% by weight; the same applies to the following component elements) is set to 2%, and the Si concentration exceeds 2%. It is discriminated as a casting material ADC12 including the high 4000 series.

Next, the wrought material is sorted into each alloy system. First, the lower limit of the Zn concentration of the added element is set to 2%, and those exceeding 2% are determined to be 7000 series.

Subsequently, the lower limit of the Cu concentration is set to 1.5%, and those exceeding 1.5% are determined to be 2000 series.

Subsequently, the lower limit of the Mg concentration is set to 1.5%, and those exceeding 1.5% are determined to be 5000 series.

Finally, the lower limit of the Mn concentration is set to 0.5%, those exceeding 0.5% are discriminated as 3000 series, and those exceeding 0.5% are 6000 series including 1000 series. To determine.

If necessary, the metal scrap M determined to be the 6000 series can be further determined. The upper limit of the Mg concentration is set to 0.3%, and those having a Mg concentration of less than 0.3% are judged to be 1000 series, and those having a Mg concentration of 0.3% or more are judged to be 6000 series.

Further, it is possible to discriminate the alloy type in more detail by paying attention to other component elements. When discriminating the 8000 series, after discriminating the 3000 series, the lower limit of the Fe concentration is set to 0.6%, and the one exceeding 0.6% is discriminated as the 8000 series, and 0.6. % Or less is discriminated as 6000 series including 1000 series.

The threshold value of the concentration of the component element used for the above determination can be appropriately set to an appropriate value according to a change in the standard or the like.

The determination result of the alloy type of the metal scrap M is associated with the stored cell information and sent from the calculation unit 14a to the sorting device 3.

The aluminum alloy scrap after discriminating the alloy type is carried out from the metal scrap discriminating device 1 by the transport device 2 and sent to the sorting device 3.

The sorting device 3 sorts the metal scrap M carried out from the metal scrap discriminating device 1 for each alloy type based on the discriminating result of the alloy type to be discriminated sent from the metal scrap discriminating device 1. For scrap distribution, there is a "receiver" method in which the scrap receiving port prepared for the alloy type moves with respect to the cell according to the discrimination result, or the scrap receiving port for the alloy type is fixed and the metal scrap M is discriminated from the cell. Various methods can be adopted, such as a "drop" method in which the product is dropped into the receiving port that matches the result.

(Change example)
The method for discriminating metal scrap of the present invention can also be applied to discriminating various metal scraps such as iron-based materials. For example, the determination of metal scrap made of an iron-based material can be performed by paying attention to the component elements Ni, Cr, Mo, Mn and the like.

According to the method for discriminating metal scrap of the present invention, since accurate analysis can be performed quickly and accurately only by irradiating the metal scrap M once, the alloy is irradiated with the laser light without stopping the metal scrap M. The species can be identified.

(Effect of embodiment)
According to the method for discriminating metal scrap and the metal scrap discriminating device 1 of the present invention, the focal distance for concentrating the irradiated laser beam L on the metal scrap corresponds to the variation in the shape of the metal scrap, and the energy density of the laser beam is high. Since the distance is set so that the concentration of the component elements can be analyzed, the change in the area of the irradiated laser beam can be made small with respect to the change in the height of the metal scrap, so the energy density. Fluctuations can be reduced. Further, the intensity ratio between the spectral line intensity of the component element and the spectral line intensity of the main component to be discriminated is hardly affected by the height of the metal scrap. As a result, the constituent elements can be analyzed with almost no influence on the shape of the metal scrap, and the alloy type can be accurately determined.

The method for discriminating metal scrap of the present invention can be suitably used for discriminating metal scrap made of an aluminum alloy. A discrimination method that utilizes the difference in the concentration of the main additive elements that is characteristic of the alloy system of aluminum alloys is adopted, and the casting material and the wrought material can be sequentially discriminated as each alloy system by one laser irradiation. It is possible to efficiently determine the alloy type.

By combining the metal scrap discriminating device 1 with the transport device 2 and the sorting device 3, the metal scrap sorting system S is constructed in which the alloy type of the metal scrap M is discriminated by the metal scrap discriminating method of the present invention and is sorted for each alloy type. be able to.

In order to verify the effect of the present invention, a discrimination test of aluminum alloy scrap was conducted.

(Metal scrap sorting equipment)
Table 2 shows the specifications of the metal scrap discriminating device used in the examples. As the laser light, Nd: YAG laser light was used, and as the objective lens, a long focal length convex lens having a focal length of 600 mm was used. As the spectroscope, a spectroscope having a wide measurement wavelength range is used so that the spectra of Al, Si, Zn, Cu, Mg and Mn, which are component elements necessary for discriminating the aluminum alloy, can be measured. In this embodiment, the measurement wavelength range is 245-680 nm, and the spectral lines of multiple elements can be measured at the same time.

The laser beam was operated at a repetition frequency of 10 Hz, and the exposure time of the spectroscope was set to 100 ms. The spectral line intensity was taken as the intensity when one shot of the laser beam was used.

(sample)
Standard samples include aluminum alloy standard samples for emission analysis of Nippon Light Metal Co., Ltd. (AC1A, AC2B, AC3A, AC4C, AC5A, ADC10, ADC12, 3SNDC2, 7075NDC2) and ALCOA's aluminum standard sample Cu series (CU-1B). , CU-2B, CU-3B, CU-4A, SA-1973, CU-6D, CU-7B). The composition of the main additive elements of these 16 standard samples is shown in Table 3. In addition, in order to identify the analysis lines of the component elements (Cu, Si, Zn, Mg, Mn) used for sorting aluminum alloy scrap, copper (purity 99.9%), silicon (99.999%), zinc (purity 99.9%) and zinc (purity 99.9%) of pure metal samples were used. 99.5%), magnesium (99.95%), manganese (99.9%) and aluminum (99.9%) were used. As the aluminum alloy for sorting, a scrap sample containing a casting material and a wrought material was used.

(Laser light energy and spectral line intensity)
In LIPS, the spectral line intensity largely depends on the laser beam energy, and in particular, due to the influence of gas breakdown in the atmosphere, the spectral line intensity may not necessarily increase even if the laser beam energy is increased. Therefore, first, the relationship between the laser light energy and the spectral line intensity was investigated. FIG. 6 is an example of the emission spectrum observed when the laser light energy is 30 mJ, 60 mJ, and 90 mJ. An aluminum standard sample (CU-7B) was used as the sample. In both cases, spectral lines of the parent aluminum and the constituent element copper are observed, but the spectral line intensity at laser light energies of 60 mJ and 90 mJ is lower than that at 30 mJ. .. On the other hand, the background increases with the laser beam energy.

In order to quantitatively evaluate the effect of the laser light energy on the emission spectrum, the laser light energy was changed from 10 mJ to 100 mJ, and the intensity and background of the copper spectral line Cu I 521.8 nm were measured. FIG. 7 shows the measurement results. The spectral line intensity increases with the laser beam energy, reaches a maximum near 30 mJ, and then decreases. On the other hand, the background increases in proportion to the laser light energy from around 20 mJ. The cause of such a phenomenon is the breakdown plasma of the atmospheric gas generated above the sample. That is, if the laser light energy is made too large in the atmosphere, the laser light energy is absorbed by the breakdown plasma of the air, the ablation efficiency of the sample is reduced, and the background light emission is increased. This is also because the intensity of the nitrogen spectral line N II 500 nm, which is slightly observed at the laser light energy of 30 mJ in the spectrum of Fig. 6, increases sharply at 60 mJ and 90 mJ. it is obvious.

In addition to the spectral line intensity, it is important that the ratio LBR (Line-to-background ratio) to the background is large. FIG. 8 is a plot of LBR calculated using the results of FIG. 7 against laser light energy. From this result, it can be seen that the laser light energy of LBR is maximum at around 30 mJ, similar to the spectral line intensity. The spectral line intensity at 30 mJ is about twice that at 100 mJ, while the LBR is about 7 times. Therefore, the laser light energy was set to 30 mJ.

(Sample height and spectral line intensity)
Since the aluminum alloy scrap to be analyzed has various shapes, the height differs for each sample and the observed spectral line intensity changes. Therefore, the relationship between the sample height and the spectral line intensity was investigated. The height of the sample was changed by moving the sample stage up and down, and the height when the sample surface was at the focal position of the objective lens was set to 0 mm.
Fig. 9 shows the measurement results of the spectral line intensity when the height of the sample was changed from 0 mm to 20 mm. Spectral line Al I 396.1 nm. In each case, the spectral line intensity decreases as the height of the sample increases. This is because when the sample is moved upward, the beam diameter of the laser beam on the sample surface becomes large and the laser beam power density decreases. Changes in spectral line intensity due to differences in sample height reduce the accuracy of quantitative analysis, so it is necessary to keep the sample height constant during analysis, but scrap samples have different thicknesses depending on the location. It is difficult to always analyze at a constant sample height.

However, as can be seen from FIG. 9, since the changes in the spectral line intensities of copper and aluminum show almost the same tendency, the changes in the spectral line intensities due to the difference in the sample height are obtained by taking the ratio of the two. Can be expected to be corrected. Therefore, the spectral line intensity ratio of copper and aluminum at each sample height was calculated. As a result, as shown in FIG. 10, it can be seen that the intensity ratio is not affected by the sample height and the amount of defocus is almost constant in a wide range of 20 mm on one side. From this result, it was decided to use the intensity ratio of the spectral line of the component element and the spectral line of the base aluminum for the component analysis of the aluminum alloy scrap sample.

(Calibration curve)
A calibration curve was created by plotting the relationship between the concentration of each component element and the spectral line intensity using a standard sample.

First, a calibration curve of Cu, which is one of the constituent elements, was created. The results are shown in FIG. Cu I 521.8 nm and Cu I 324.7 nm are used as the spectral lines for analysis, and the intensity ratio of the aluminum spectral line Al I 396.1 nm is plotted on the vertical axis and the copper concentration is plotted on the horizontal axis. The spectral line intensity is the average value of 10 measurements, and the aluminum standard sample of ALCOA was used as the standard sample. When Cu I 521.8 nm is used for the analysis line, the spectral line intensity ratio increases linearly in proportion to the element concentration, whereas when Cu I 324.7 nm, it is due to the effect of self-absorption of the spectral line. The calibration curve is curved. However, in the copper concentration range (-5%) contained in the aluminum alloy, the change in spectral line intensity with respect to the element concentration is larger in Cu I 324.7 nm than in Cu I 521.8 nm, and the intensity is also about twice as high. There is. In addition, the spectral line Cu I 521.8 nm is affected by the background and nitrogen spectra caused by air breakdown, which can reduce the accuracy of spectral line intensity analysis when the copper concentration is low. Therefore, Cu I 324.7 nm (Fig. 11 (B)) was used for the copper analysis line.

Similarly, using the aluminum standard sample for emission analysis of Nippon Light Metal Co., Ltd. as the standard sample, the spectral lines of Si, Zn, Mg and Mn of other component elements were investigated, and Si I was used as the analysis line for each element. 288.1 nm, Zn I 334.5 nm, Mg I 383.8 nm and Mn I 403.0 nm were selected. FIG. 12 shows the calibration curve of each element.

A good proportional relationship was observed between the concentration of the constituent elements and the spectral line intensity ratio except in the region where the concentration of Mn was extremely low. This enables component analysis using the calibration curve of aluminum alloy scrap.

When a spectroscope having a measurement wavelength range of 200 to 400 nm and a high wavelength resolution is used as the spectroscope, more accurate spectral line intensity measurement becomes possible. At this time, 206.1 nm and 285.2 nm, which are more accurate spectral lines, can be adopted as the analysis lines of Zn and Mg, respectively.

(Aluminum alloy discrimination)
A discrimination test was performed based on the flowchart of FIG. Three types of casting materials (AC1A, AC2B, ADC12) and two types of wrought materials (3SNDC, 7075) were used as samples from the standard aluminum alloy sample. Table 4 shows the concentration of the principal component element and the discrimination result obtained by analyzing each sample twice. The casting material is classified as ADC12, and the wrought material is classified as an alloy system according to the main component elements. Since AC1A of the cast material has a Si concentration of less than 2%, it is classified as a 2000 series of wrought material. From this result, it was confirmed that each sample was discriminated as an alloy system corresponding to the additive element, and the aluminum alloy could be discriminated based on the flowchart of FIG.

Next, the actual scrap samples were sorted. FIG. 13 shows an aluminum alloy scrap sample used in the sorting test. The number of aluminum alloy scrap samples is 121 in total, including 7 cast alloys and 114 wrought 6000 alloys. Serial numbers from 1 to 7 for casting samples and 8 to 121 for wrought material 6000 samples were entered, and analysis and sorting were performed. As a result, it was confirmed that the samples 1 to 7 were sorted as a casting material (ADC12), and the remaining 114 samples were all sorted as a 6000 series, and scrap samples having different shapes and thicknesses could be sorted.

1 ... Metal scrap discrimination device 2 ... Conveyor device 3 ... Sorting device 10 ... Laser oscillator 11 ... Objective lens 12 ... Condensing means 13 ... Spectroscopy 14 ... Processing system 14a ... Calculation unit 14b ... Control unit 15 ... Pulse generator L ... Laser Light M ... Metal scrap P ... Laser-induced plasma S ... Metal scrap sorting system

Claims (7)

It is a method for discriminating metal scrap using laser inductively coupled plasma emission spectrometry.
A process of condensing and irradiating laser light for generating laser-induced plasma on metal scrap to be discriminated.
The process of obtaining the emission spectrum by splitting the synchrotron radiation from the laser-induced plasma generated by the irradiation of the laser beam, and
A step of calculating the concentration of the component element based on the spectral line intensity of the component element used for the preset discrimination, and a step of calculating the concentration of the component element.
A step of discriminating the alloy type to be discriminated based on the concentration of each component element is provided.
The focal distance for concentrating the irradiated laser light on the metal scrap has a small effect on the fluctuation of the energy density of the laser light due to the fluctuation of the distance between the metal scrap surface and the light source of the laser light due to the variation in the shape of the metal scrap. The long focal length is set so that the energy density of the laser beam is fixed at a distance that is the energy density at which the concentration analysis of the constituent elements is possible.
A method for discriminating metal scrap, wherein the concentration of a component element is calculated based on the intensity ratio between the spectral line intensity of the component element and the spectral line intensity of the main component to be discriminated. The metal scrap according to claim 1, wherein the energy density of the laser beam to be irradiated is set to an energy density at which the breakdown plasma of the atmospheric gas in the measurement environment does not interfere with the measurement of the spectral line intensity of the constituent elements. Discrimination method. The method for determining metal scrap according to claim 1 or 2, wherein the metal scrap is an aluminum alloy. The method for discriminating metal scrap according to claim 3, wherein the component elements used for discrimination are Si, Zn, Cu, Mg and Mn. The discrimination of metal scrap according to claim 4, wherein the corresponding alloy type is sequentially discriminated based on the discriminating conditions set at each concentration in the order of each concentration of Si, Zn, Cu, Mg and Mn. Method. A metal scrap discriminator that discriminates metal scrap using a laser-induced plasma emission spectrometry method.
A laser oscillator that outputs laser light and
An objective lens that focuses and irradiates the metal scrap to be discriminated with the laser light output from the laser oscillator.
A condensing means that collects the radiated light emitted from the laser-induced plasma that is irradiated with the laser light and generated from the metal scrap.
A spectroscope that disperses the synchrotron radiation collected by the condensing means and acquires an emission spectrum.
A calculation processing means for calculating the concentration of the component element used for the preset discrimination based on the spectral line intensity of the emission spectrum acquired by the spectroscope and discriminating the alloy type of the metal scrap is provided.
The focal distance of the objective lens is a long focal length in which the influence of the fluctuation of the distance between the metal scrap surface and the light source of the laser beam due to the variation in the shape of the metal scrap on the fluctuation of the energy density of the laser beam is small. The energy density of the laser beam is fixed at a distance that makes it possible to analyze the concentration of the constituent elements.
A metal scrap discriminating device according to any one of claims 1 to 5, wherein the metal scrap discriminating method is configured to be feasible. The metal scrap discriminating device according to claim 6 and
A transport device that transports metal scrap to the metal scrap discriminating device and carries out the metal scrap after discriminating the alloy type from the metal scrap discriminating device.
A metal scrap sorting system including a sorting device for sorting metal scrap carried out from the metal scrap sorting device for each alloy type.

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